Method and apparatus for controlling an airbag

ABSTRACT

Method and system for controlling deployment of an airbag in which the position of an occupant to be protected by deployment of the airbag is determined, the probability that a crash requiring deployment of the airbag is occurring is assessed and deployment of the airbag enabled in consideration of the determined position of the occupant and the assessed probability that a crash is occurring. Deployment of the airbag may be enabled by analyzing the assessed probability relative to a pre-determined threshold whereby deployment of the airbag is enabled only when the assessed probability is greater than the threshold. The threshold may be adjusted based on the determined position of the occupant.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. patentapplication Ser. No. 09/778,137 which in turn is a continuation of U.S.patent application Ser. No. 08/905,877 filed Aug. 4, 1997, now U.S. Pat.No. 6,186,537, which in turn is a continuation of U.S. patentapplication Ser. No. 08/505,036 filed Jul. 25, 1995, now U.S. Pat. No.5,653,462, which in turn is a continuation of U.S. patent applicationSer. No. 08/040,978 filed Mar. 31, 1993, now abandoned, which in turn isa continuation-in-part of U.S. patent application Ser. No. 07/878,571filed May 5, 1992, now abandoned.

FIELD OF THE INVENTION

[0002] The present invention relates to methods and apparatus fordisabling an airbag system in a motor vehicle if the seating position isunoccupied or an occupant is out-of-position, i.e., closer to the airbagdoor than a predetermined distance

BACKGROUND OF THE INVENTION

[0003] Crash sensors for determining that a vehicle is in a crash ofsufficient magnitude as to require the deployment of an inflatablerestraint system, or airbag, are either mounted in a portion of thefront of the vehicle which has crushed by the time that sensortriggering is required, the crush zone, or elsewhere such as thepassenger compartment, the non-crush zone. Regardless of where sensorsare mounted there will always be crashes where the sensor triggers lateand the occupant has moved to a position near to the airbag deploymentcover In such cases, the occupant may be seriously injured or evenkilled by the deployment of the airbag This invention is largelyconcerned with preventing such injuries and deaths by preventing lateairbag deployments.

[0004] In a Society of Automotive Engineers (SAE) paper by Mertz,Driscoll, Lenox, Nyquist and Weber titled “Response of Animals Exposedto Deployment of Various Passenger Inflatable Restraint System Conceptsfor a Variety of Collision Severities and Animal Positions” SAE 826074,1982, the authors show that an occupant can be killed or seriouslyinjured by the airbag deployment if he or she is located out of positionnear or against the airbag when deployment is initiated. Theseconclusions were again reached in a more recent paper by Lau, Horsch,Viano and Andrzejak titled “Mechanism of Injury From Air Bag DeploymentLoads”, published in Accident Analysis & Prevention, Vol. 25, No.1,1993, Pergamon Press, New York, where the authors conclude that “Even aninflator with inadequate gas output to protect a properly seatedoccupant had sufficient energy to induce severe injuries in a surrogatein contact with the inflating module.” These papers highlight theimportance of preventing deployment of an airbag when an occupant is outof position and in close proximity to the airbag module.

[0005] The Ball-in-Tube crush zone sensor, such as disclosed in U.S.Pat. Nos. 4,974,350; 4,198,864; 4,284,863; 4,329,549, 4,573,706 and4,900,880 to D S. Breed, has achieved the widest use while othertechnologies, including magnetically damped sensors as disclosed in U.S.Pat. No. 4,933,515 to Behr et al and crush switch sensors such asdisclosed in U.S. Pat. No. 4,995,639 to D S. Breed, are now becomingavailable. Other sensors based on spring-mass technologies are alsobeing used in the crush zone. Crush zone mounted sensors, in order tofunction properly, must be located in the crush zone at the requiredtrigger time during a crash or they can trigger late. One example ofthis was disclosed in a Society of Automotive Engineers (SAE) paper byD. S. Breed and V. Castelli titled “Trends in Sensing Frontal Impacts”,SAE 890750, 1989, and further in U.S. Pat. No 4,900,880. In impacts withsoft objects, the crush of a vehicle can be significantly less than forimpacts with barriers, for example. In such cases, even at moderatevelocity changes where an airbag might be of help in mitigatinginjuries, the crush zone mounted sensor might not actually be in thecrush zone at the time that sensor triggering is required for timelyairbag deployment, and as a result can trigger late when the occupant isalready resting against the airbag module.

[0006] There is a trend underway toward the implementation of SinglePoint Sensors (SPS) which are typically located in the passengercompartment In theory, these sensors use sophisticated computeralgorithms to determine that a particular crash is sufficiently severeas to require the deployment of an airbag. In another SAE paper byBreed, Sanders and Castelli titled “A Critique of Single Point Sensing”,SAE 920124, 1992, which is incorporated herein by reference, the authorsdemonstrate that there is insufficient information in the non-crush zoneof the vehicle to permit a decision to be made to deploy an airbag intime for many crashes. Thus, sensors mounted in the passengercompartment or other non-crush zone locations, will also trigger thedeployment of the airbag late on many crashes.

[0007] A crash sensor is necessarily a predictive device. In order toinflate the airbag in time, the inflation must be started before thefull severity of the crash has developed. All predictive devices aresubject to error, so that sometimes the airbag will be inflated when itis not needed and at other times it will not be inflated when it couldhave prevented injury. The accuracy of any predictive device can improvesignificantly when a longer time is available to gather and process thedata. One purpose of the occupant position sensor is to make possiblethis additional time in those cases where the occupant is farther fromthe steering wheel when the crash begins and/or where, due to seat beltuse or otherwise, the occupant is moving toward the steering wheel moreslowly In these cases the decision on whether to deploy the airbag canbe deferred and a more precise determination made of whether the airbagis needed.

[0008] The discussions of timely airbag deployment above are all basedon the seating position of the average male (the so called 50% male)relative to the airbag or steering wheel. For the 50% male, the sensortriggering requirement is typically calculated based on an allowablemotion of the occupant of 5 inches before the airbag is fully inflated.Airbags typically require about 30 milliseconds of time to achieve fullinflation and, therefore, the sensor must trigger inflation of theairbag 30 milliseconds before the occupant has moved forward 5 inchesThe 50% male, however, is actually the 70% person and therefore about70% of the population sit on average closer to the airbag than the 50%male and thus are exposed to a greater risk of interacting with thedeploying airbag. A recent informal survey, for example, found thatalthough the average male driver sits about 12 inches from the steeringwheel, about 2% of the population of drivers sit closer than 6 inchesfrom the steering wheel and 10% sit closer than 9 inches. Also, about 1%of drivers sit at about 24 inches and about 16% at least 18 inches fromthe steering wheel. None of the sensor systems now on the market takeaccount of this variation in occupant seating position and yet this canhave a critical effect on the sensor required maximum triggering time.

[0009] For example, if a fully inflated airbag is about 7 inches thick,measured from front to back, then any driver who is seated closer than 7inches will necessarily interact with the deploying airbag and theairbag probably should not be deployed at all. For a recently analyzed30 mph barrier crash of a mid-sized car, the sensor required triggeringtime, in order to allow the airbag to inflate fully before the driverbecomes closer than 7 inches from the steering wheel, results in amaximum sensing time of 8 milliseconds for an occupant initiallypositioned 9 inches from the airbag, 25 milliseconds at 12 inches, 45milliseconds at 18 inches and 57 milliseconds for the occupant who isinitially positioned at 24 inches from the airbag. Thus for the samecrash, the sensor required triggering time varies from a no trigger to57 milliseconds, depending on the initial position of the occupant. Asingle sensor triggering time criterion that fails to take this intoaccount, therefore, will cause injuries to small people or deny theprotection of the airbag to larger people A very significant improvementto the performance of an airbag system will necessarily result fromtaking the occupant position into account as described herein.

[0010] A further complication results from the fact that a greaternumber of occupants are now wearing seatbelts which tends to preventmany of these occupants from getting too close to the airbag. Thus, justknowing the initial position of the occupant is insufficient and eitherthe position must be continuously monitored or the seatbelt use must beknown. Also, the occupant may have fallen asleep or be unconscious priorto the crash and be resting against the steering wheel. Some sensorsystems have been proposed that double integrate the acceleration pulsein the passenger compartment and determine the displacement of theoccupant based on the calculated displacement of an unrestrainedoccupant seated at the mid seating position. This sensor system thenprevents the deployment of the airbag if, by this calculation, theoccupant is too close to the airbag. This calculation can be greatly inerror for the different seating positions discussed above and also forthe seatbelted occupant, and thus an occupant who wears a seatbelt couldbe denied the added protection of the airbag in a severe crash.

[0011] As the number of vehicles which are equipped with airbags is nowrapidly increasing, the incidence of late deployments is alsoincreasing. It has been estimated that out of approximately 400 airbagrelated complaints to the National Highway Traffic Safety Administration(NHTSA) through 1991, for example, about 5% to 10% involved bums andinjuries which were due to late airbag deployments. There is also atleast three known fatalities where a late airbag deployment is suspectedas the cause.

[0012] The need for an occupant position sensor has been observed byothers and several methods have been disclosed in U.S. patents fordetermining the position and velocity of an occupant of a motor vehicle.Each of these systems, however, have significant limitations. In Whiteet al., U.S. Pat. No. 5,071,160, for example, a single acoustic sensorand detector is disclosed and illustrated mounted lower than thesteering wheel. White et al correctly perceive that such a sensor couldbe defeated, and the airbag falsely deployed, by an occupant adjustingthe control knobs on the radio and thus they suggest the use of aplurality of such transmitter/receivers If a driver of a vehicle isseated one foot from the transmitter/receiver, and using 1128 feet persecond as the velocity of sound, it would require approximately 2milliseconds for the sound to travel to the occupant and return. The useof the same device to both transmit and detect the sound waves requiresthat the device cannot send and receive simultaneously and therefore itrequires at least 2 milliseconds to obtain a single observation of theoccupant's position. Naturally as the distance from the occupant to thesensor increases, the observation rate further decreases. For apassenger sitting two feet from the sensor, the delay is approximately 4milliseconds Sensors of this type can be used to accurately obtain theinitial position of the occupant but the determination of the occupant'svelocity, and thus the prediction of when he/she is likely to be tooclose to the deploying airbag, will necessarily be inaccurate due to thelong delay between position points and thus the small number of suchpoints available for the prediction and the inherent noise in thereflected signal.

[0013] Mattes et al., in U.S. Pat. No. 5,118,134, disclose a singleultrasonic transmitter and a separate receiver, but, no description isprovided as to the manner in which this combination is used. Inconventional ultrasonic distance measuring systems, the transmitteremits a burst of ultrasonic waves and then measures the time requiredfor the waves to bounce off the object and reach the receptor Thetransmitter does not transmit again until the waves have been receivedby the receiver. This system again suffers from the time delay of atleast 2 to 4 milliseconds described above.

[0014] Doppler techniques can be used to determine the velocity of theoccupant as disclosed below. Both White et al and Mattes et al, however,specifically state that the occupant's velocity is determined from asuccession of position measurements. The use of the Doppler effect isdisclosed in U.S. Pat. No. 3,275,975 to King, but only to determine thatthe occupant is not moving. No attempt is made by King to measure thevelocity of the occupant toward an airbag using this effect. Also noneof the references above disclose the use of an ultrasonic transmitterand receiver to simultaneously determine the position and velocity ofthe occupant using a combination of the transmission time and theDoppler effect as disclosed below.

[0015] The object of an occupant position sensor is to determine thelocation of the head and/or chest of the vehicle occupant relative tothe airbag since it is the impact of either the head or chest with thedeploying airbag which can result in serious injuries. For the purposesherein, therefore, whenever the position of the occupant is referencedit will mean the position of the head or chest of the occupant and notthat of his/her arms, hands or legs. The preferred mounting of theultrasonic transmitters, therefore, are those locations which have theclearest unimpeded view of the occupant's head and chest. Theselocations are generally at the top of the dashboard, the windshield, theheadliner above the windshield and the rear view mirror. Both White etal. and Mattes et al. disclose only lower mounting locations of theultrasonic transmitters such as on the dashboard or below the steelingwheel. Both such mounting locations are particularly prone to detectionerrors due to positioning of the occupant's hands, arms and legs. Thiswould require at least three, and preferably more, such sensors anddetectors and an appropriate logic circuitry for the case where thedriver's arms are the closest objects to two of the sensors. When anunimpeded view is not possible, some means of pattern recognition, whichis not disclosed in the above references, is required to differentiatebetween the occupant and his/her extremities such as his/her hands, armsor legs

[0016] Mattes et al. further disclose the placement of the sensor in theheadrest but such an arrangement is insufficient since it measures thedistance from the headrest to the occupant and not from the airbag.

[0017] White et al. discloses the use of error correction circuitry todifferentiate between the velocity of one of the occupant's hands as inthe case where he/she is adjusting the knob on the radio and theremainder of the occupant Three ultrasonic sensors of the type disclosedby White et al. would accomplish this differentiation if two of themindicated that the occupant was not moving while the third wasindicating that he or she was Such a combination, however, would notdifferentiate between an occupant with both hands and arms in the pathof the ultrasonic transmitter at such a location that it was blocking asubstantial view of the occupant's head or chest. Since the sizes anddriving positions of occupants are extremely varied, pattern recognitionsystems are required when a clear view of the occupant, unimpeded byhis/her extremities, cannot be guaranteed. Pattern recognition systemsfor the occupant as used here means any system which will differentiatebetween the occupant and his extremities based on relative size,position or shape. Pattern recognition systems can also be used todifferentiate an occupant from a seat or a bag of groceries also basedon relative size, position or shape or even on passive infraredradiation, as described below.

OBJECTS AND SUMMARY OF THE INVENTION

[0018] The occupant position sensor of this invention is adapted forinstallation in the passenger compartment of an automotive vehicleequipped with a passenger protective device such as an inflatableairbag. When the vehicle is subjected to a crash of sufficient magnitudeas to require deployment of the passive protective device, and thesensor system has determined that the device is to be deployed, theoccupant position sensor and associated electronic circuitry determinesthe position of the vehicle occupant relative to the airbag and disablesdeployment of the airbag if the occupant is positioned so that he/she islikely to be injured by the deploying airbag. Naturally, as discussedbelow, the addition of an occupant position sensor onto a vehicle leadsto other possibilities such as the monitoring of the driver's behaviorwhich can be used to warn a driver if he or she is falling asleep, or tostop the vehicle if the driver loses the capacity to control thevehicle.

[0019] According to a preferred implementation, an ultrasonic generatortransmits a burst of ultrasonic waves which travel to the occupant andare reflected back to a receptor, which may be the same device as thegenerator. The time period required for the waves to travel from thegenerator and return is used to determine the position of the occupantand the frequency shift of the waves is used to determine the velocityof the occupant relative to the airbag.

[0020] In another preferred implementation, infrared light is used toilluminate the occupant and lenses are used to focus images of theoccupant onto arrays of charge coupled devices (CCD). Outputs from theCCD arrays, are analyzed by appropriate logic circuitry, to determinethe position and velocity of the occupant's head and chest.

[0021] In yet another preferred implementation, a beam of radiation ismoved back and forth across the occupant illuminating various portionsof the occupant and with appropriate algorithms the position of theoccupant in the seat is accurately determined.

[0022] It is an object of the present invention to provide a method andapparatus for vehicle crash discrimination and control of a safetyrestraint having increased efficiency and reliability in actuating ordeploying the safety restraint such as an airbag.

[0023] It is another object of the present invention to provide a methodand system for vehicle crash discrimination and control of a safetyrestraint which continuously detects various vehicle occupant positionsfor optimizing a discrimination analysis to achieve increased efficiencyand reliability in actuating the safety restraint.

[0024] It is another object of the present invention to provide a methodand system for discriminating vehicle crashes and control of a safetyrestraint which adjusts a decision period used for determining when toactuate the safety restraint, wherein the adjustments are based on theposition of the occupant.

[0025] It is another object of this invention to provide an occupantposition sensor which reliably permits, and in a timely manner, adetermination to be made that he/she is out of position, or will becomeout of position, and likely to be injured by a deploying airbag.

[0026] It is also an object of this invention to provide a system whichwill accurately discriminate between the occupant's head or chest andother parts of the body in determining the occupant's position andvelocity.

[0027] It is another object of this invention to independently preventthe deployment of the driver or passenger airbags if either occupant isout of position.

[0028] It is still another object of this invention to provide for amore complete analysis of an occupant through the use of CCD's tocapture more of the occupant's image.

[0029] Another object of this invention is to provide a warning to adriver if he/she is falling asleep.

[0030] Still another object of this invention is to sense that a driveris inebriated or otherwise suffering from a reduced capacity to operatea motor vehicle and to take appropriate action.

[0031] In order to achieve one or more of these objects, a method forcontrolling deployment of an airbag comprises the steps of determiningthe position of an occupant to be protected by deployment of the airbag,assessing the probability that a crash requiring deployment of theairbag is occurring and enabling deployment of the airbag inconsideration of the determined position of the occupant and theassessed probability that a crash is occurring. Deployment of the airbagmay be enabled by analyzing the assessed probability relative to apredetermined threshold whereby deployment of the airbag is enabled onlywhen the assessed probability is greater than the threshold. Thethreshold may be adjusted based on the determined position of theoccupant

[0032] The position of the occupant may be determined in various waysincluding by receiving and analyzing waves from a space in a passengercompartment of the vehicle occupied by the occupant, transmitting wavesto impact the occupant, receiving waves after impact with the occupantand measuring time between transmission and reception of the waves,obtaining two or three-dimensional images of a passenger compartment ofthe vehicle occupied by the occupant and analyzing the images with anoptional focusing of the images prior to analysis, or by moving a beamof radiation through a passenger compartment of the vehicle occupied bythe occupant. The waves may be ultrasonic, radar, electromagnetic,passive infrared, and the like, and capacitive in nature. In the lattercase, a capacitance or capacitive sensor may be provided. An electricfield sensor could also be used

[0033] Deployment of the airbag can be disabled when the determinedposition is too close to the airbag

[0034] The rate at which the airbag is inflated and/or the time in whichthe airbag is inflated may be determined based on the determinedposition of the occupant.

[0035] Another method for controlling deployment of an airbag comprisesthe steps of determining the position of an occupant to be protected bydeployment of the airbag and adjusting a threshold used in a sensoralgorithm which enables or suppresses deployment of the airbag based onthe determined position of the occupant. The probability that a crashrequiring deployment of the airbag is occurring may be assed andanalyzed relative to the threshold whereby deployment of the airbag isenabled only when the assessed probability is greater than thethreshold. The position of the occupant can be determined in any of theways mentioned above.

[0036] A system for controlling deployment of an airbag comprisesdetermining means for determining the position of an occupant to beprotected by deployment of the airbag, sensor means for assessing theprobability that a crash requiring deployment of the airbag isoccurring, and circuit means coupled to the determining means, thesensor means and the airbag for enabling deployment of the airbag inconsideration of the determined position of the occupant and theassessed probability that a crash is occurring. The circuit means arestructured and arranged to analyze the assessed probability relative toa pre-determined threshold whereby deployment of the airbag is enabledonly when the assessed probability is greater than the threshold.Further, the circuit means are arranged to adjust the threshold based onthe determined position of the occupant. The determining means may anyof the determining systems discussed above

[0037] Another system for controlling deployment of an airbag comprisesa crash sensor for providing information on a crash involving thevehicle, a position determining arrangement for determining the positionof an occupant to be protected by deployment of the airbag and a circuitcoupled to the airbag, the crash sensor and the position determiningarrangement and arranged to issue a deployment signal to the airbag tocause deployment of the airbag The circuit is arranged to consider adeployment threshold which varies based on the determined position ofthe occupant. Further, the circuit is arranged to assess the probabilitythat a crash requiring deployment of the airbag is occurring and analyzethe assessed probability relative to the threshold whereby deployment ofthe airbag is enabled only when the assessed probability is greater thanthe threshold.

[0038] Other objects and advantages of the present invention will becomeapparent from the following description of the preferred embodimentstaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The accompanying drawings, which are incorporated into and form apart of the specification, illustrate several embodiments of the presentinvention and, together with the following description, serve to explainthe principles of the invention The drawings are for the purpose ofillustrating preferred embodiments of the invention only and are not tobe construed as limiting the inventions.

[0040]FIG. 1 is a side view, with certain portions removed or cut away,of a portion of the passenger compartment of a vehicle showing severalpreferred mounting locations of occupant position sensors for sensingthe position of the vehicle driver.

[0041]FIG. 2 is a cross section view of a steering wheel and airbagmodule assembly showing a preferred mounting location of an ultrasonicwave generator and receiver.

[0042]FIG. 3 is a side view, with certain portions removed or cut away,of a portion of the passenger compartment of a vehicle showing preferredmounting locations of the occupant position sensor employing multipletransmitters and receivers

[0043]FIG. 4 is a side view, with certain portions removed or cut away,of a portion of the passenger compartment of a vehicle showing anoccupant position sensor used in combination with a reflectivewindshield for sensing the position of the vehicle passenger.

[0044]FIG. 5 is a partial cutaway view of a seatbelt retractor with aspool out sensor utilizing a shaft encoder

[0045]FIG. 6 is a side view of a portion of a seat and seat rail showinga seat position sensor utilizing a potentiometer

[0046]FIG. 7 is a circuit schematic illustrating the use of the occupantposition sensor in conjunction with the remainder of the inflatablerestraint system.

[0047]FIG. 8 is a schematic illustrating the circuit of an occupantposition-sensing device using a modulated infrared signal, beatfrequency and phase detector system

[0048]FIG. 9 is a flowchart of a method for controlling an airbag inaccordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] Referring now to the drawings, a section of the passengercompartment of an automobile is shown generally as 100 in FIG. 1. Adriver of a vehicle 101 sits on a seat 102 behind a steering wheel 103which contains an airbag assembly 104. Five transmitter and/or receiverassemblies 110, 111, 112, 113 and 114 are positioned at various placesin the passenger compartment to determine the location of the head,chest and torso of the driver relative to the airbag. Usually, in anygiven implementation, only one or two of the transmitters and receiverswould be used depending on their mounting locations as described below.

[0050]FIG. 1 illustrates several of the possible locations of suchdevices. For example, transmitter and receiver 110 emits ultrasonicacoustical waves which bounce off the chest of the driver and return.

[0051] Periodically a burst of ultrasonic waves at about 50 kilohertz isemitted by the transmitter/receiver and then the echo, or reflectedsignal, is detected by the same or different device. An associatedelectronic circuit measures the time between the transmission and thereception of the ultrasonic waves and thereby determines the distancefrom the transmitter/receiver to the driver based on the velocity ofsound. This information is then sent to the crash sensor and diagnosticcircuitry which determines if the driver is close enough to the airbagthat a deployment might, by itself, cause injury to the driver. In sucha case, the circuit disables the airbag system and thereby prevents itsdeployment In an alternate case, the sensor algorithm assesses theprobability that a crash requiring an airbag is in process and waitsuntil that probability exceeds an amount that is dependent on theposition of the occupant. Thus, for example, the sensor might decide todeploy the airbag based on a need probability assessment of 50%, if thedecision must be made immediately for an occupant approaching theairbag, but might wait until the probability rises to 95% for a moredistant occupant. This aspect of the invention is described in detailbelow with reference to FIG. 9. Although a driver system has beenillustrated, the passenger system would be identical

[0052] In another implementation, the sensor algorithm may determine therate that gas is generated to affect the rate that the airbag isinflated In all of these cases the position of the occupant is used toaffect the deployment of the airbag either as to whether or not itshould be deployed at all, the time of deployment or as to the rate ofinflation

[0053] The ultrasonic transmitter/receiver 110 is similar to that usedon modem auto-focus cameras such as manufactured by the PolaroidCorporation Other camera auto-focusing systems use differenttechnologies, which are also applicable here, to achieve the samedistance to object determination One camera system manufactured by Fujiof Japan, for example, uses a stereoscopic system which could also beused to determine the position of a vehicle occupant providing there issufficient light available. In the case of insufficient light, a sourceof infrared light can be added to illuminate the driver. In a relatedimplementation, a source of infrared light is reflected off of thewindshield and illuminates the vehicle occupant. An infrared receiver114 is located attached to the rear view mirror 105, as shown in FIG. 1.Alternately, the infrared could be sent by the device 114 and receivedby a receiver elsewhere. Since any of the devices shown in FIGS. 1 and 3could be either transmitters or receivers or both, for simplicity, onlythe transmitted and not the reflected wave fronts are illustrated.

[0054] In the above-described system, a lens within receptor 114captures the reflected infrared light from the head or chest of thedriver and displays it onto a charge coupled device (CCD) array. Onetype of CCD is that used in television cameras to convert an image intoan electrical signal. For the purposes herein a CCD will be used toinclude all devices which are capable of converting light frequencies,including infrared, into electrical signals The CCD is scanned and thefocal point of the lens is altered, under control of an appropriatecircuit, until the sharpest image of the driver's head or chest resultsand the distance is then known from the focusing circuitry The precisionof this measurement is enhanced if two receptors are used which caneither project images onto a single CCD or on separate CCD's. In thefirst case, one of the lenses could be moved to bring the two imagesinto coincidence while in the other case the displacement of the imagesneeded for coincidence would be determined mathematically. Naturally,other systems could be used to keep track of the different images suchas the use of filters creating different infrared frequencies for thedifferent receptors and again using the same CCD array. In addition togreater precision in determining the location of the occupant, theseparation of the two receptors can also be used to minimize the effectsof hands, arms or other extremities which might be very close to theairbag. In this case, where the receptors are mounted high on thedashboard on either side of the steering wheel, an arm, for example,would show up as a thin object but much closer to the airbag than thelarger body parts and, therefore, easily distinguished and eliminated,permitting the sensors to determine the distance to the occupant'schest. This is one example of the use of pattern recognition.

[0055] An optical infrared transmitter and receiver assembly is showngenerally at 112 in FIG. 1 and is mounted onto the instrument panelfacing the windshield. Although not shown in this view, reference 112consists of three devices, one transmitter and two receivers, one oneach side of the transmitter. In this case the windshield is used toreflect the illumination light, and also the light reflected back by thedriver, in a manner similar to the “heads-up” display which is now beingoffered on several automobile models. The “heads-up” display, of course,is currently used only to display information to the driver and is notused to reflect light from the driver to a receiver In this case, thedistance to the driver is determined stereoscopically through the use ofthe two receivers In its most elementary sense, this system can be usedto measure the distance of the driver to the airbag module. In moresophisticated applications, the position of the driver, and particularlyof the drivers head, can be monitored over time and any behavior, suchas a drooping head, indicative of the driver falling asleep or of beingincapacitated by drugs, alcohol or illness can be detected andappropriate action taken. Other forms of radiation including visuallight, radar and microwaves as well as high frequency ultra sound couldalso be used by those skilled in the art.

[0056] Particular mention should be made of the use of radar sinceinexpensive single axis antennas are now readily available. A scanningradar beam is used in this implementation and the reflected signal isreceived by a single axis phase array antenna to generate an image ofthe occupant for input into the appropriate pattern detection circuitry.The word circuitry as used herein includes, in addition to normalelectronic circuits, a microprocessor and appropriate software.

[0057] Electromagnetic or ultrasonic energy can be transmitted in threemodes in determining the position of an occupant. In most of the casesdisclosed above, it is assumed that the energy will be transmitted in abroad diverging beam which interacts with a substantial portion of theoccupant. This method has the disadvantage that it will reflect firstoff the nearest object and, especially if that object is close to thetransmitter, it may mask the true position of the occupant. This can bepartially overcome through the use of the second mode which uses anarrow beam. In this case, several narrow beams are used. These beamsare aimed in different directions toward the occupant from a positionsufficiently away from the occupant that interference is unlikely. Asingle receptor could be used providing the beams are either cycled onat different times or arc of different frequencies Another approach isto use a single beam emanating from a location which has an unimpededview of the occupant such as the windshield header. If two spaced apartCCD array receivers are used, the angle of the reflected beam can bedetermined and the location of the occupant can be calculated The thirdmode is to use a single beam in a manner so that it scans back and forthor up and down, or in some other pattern, across the occupant. In thismanner, an image of the occupant can be obtained using a single receptorand pattern recognition software can be used to locate the head or chestof the occupant. The beam approach is most applicable to electromagneticenergy but high frequency ultra sound can also be formed into a narrowbeam.

[0058] The windshield header as used herein includes the space above thefront windshield including the first few inches of the roof.

[0059] A similar effect to modifying the wave transmission mode can alsobe obtained by varying the characteristics of the receptors. Throughappropriate lenses or reflectors, receptors can be made to be mostsensitive to radiation emitted from a particular direction. In thismanner a single broad beam transmitter can be used coupled with an arrayof focused receivers to obtain a rough image of the occupant.

[0060] Each of these methods of transmission or reception could be used,for example, at any of the preferred mounting locations shown in FIG. 1.

[0061] Another preferred location of a transmitter/receiver for use withairbags is shown at 111 in FIG. 1. In this case, the device is attachedto the steering wheel and gives an accurate determination of thedistance of the driver's chest from the airbag module Thisimplementation would generally be used with another device such as 110at another location.

[0062] Alternate mountings for the transmitter/receiver include variouslocations on the instrument panel on either side of the steering columnsuch as 113 in FIG. 1.

[0063] The location or position of the occupant can be determined invarious ways as noted and listed above and below as well Generally, anytype of occupant sensor can be used. Mention is made of some particularoccupant sensors which can be used in the systems and methods inaccordance with the invention. Specifically, a camera or other devicefor obtaining images of a passenger compartment of the vehicle occupiedby the occupant and analyzing the images can be mounted at the locationsof the transmitter and/or receiver assemblies 110-114. The camera orother device may be constructed to obtain three-dimensional imagesand/or focus the images on one or more optical arrays such as CCDs.Further, a mechanism for moving a beam of radiation through a passengercompartment of the vehicle occupied by the occupant, i.e., a scanningsystem, can be used When using ultrasonic or radar waves, the time offlight between the transmission and reception of the waves can be usedto determine the position of the occupant. The occupant sensor can alsobe arranged to receive infrared radiation from a space in a passengercompartment of the vehicle occupied by the occupant It can also comprisean electric field sensor operative in a seat occupied by the occupant ora capacitance sensor operative in a seat occupied by the occupant. Theimplementation of such sensors in the invention will be readilyappreciated by one skilled in the art in view of the disclosure hereinof general occupant sensors for sensing the position of the occupantusing waves, energy or radiation.

[0064] Also, although some of the devices herein illustrated assume thatfor the ultrasonic system the same device would be used for bothtransmitting and receiving waves, there are advantages in separatingthese functions. Since there is a time lag required for the system tostabilize after transmitting a pulse before it can receive a pulse,close measurements are enhanced, for example, by using separatetransmitters and receivers In addition, if the ultrasonic transmitterand receiver are separated, the transmitter can transmit continuouslyproviding the transmitted signal is modulated in such a manner that thereceived signal can be compared with the transmitted signal to determinethe time it took for the waves to reach and reflect off of the occupantMany methods exist for this modulation including varying the frequencyor amplitude of the waves or by pulse modulation or coding In all cases,the logic circuit which controls the sensor and receiver must be able todetermine when the signal which was most recently received wastransmitted. In this manner, even though the time that it takes for thesignal to travel from the transmitter to the receiver, via reflectionoff of the occupant, may be several milliseconds, information as to theposition of the occupant is received continuously which permits anaccurate, although delayed, determination of the occupant's velocityfrom successive position measurements Conventional ultrasonic distancemeasuring devices must wait for the signal to travel to the occupant andreturn before a new signal is sent. This greatly limits the frequency atwhich position data can be obtained to the formula where the frequencyis equal to the velocity of sound divided by two times the distance tothe occupant. For example, if the velocity of sound is taken at about1000 feet per second, occupant position data for an occupant located onefoot from the transmitter can only be obtained every 2 millisecondswhich corresponds to a frequency of 500 cycles per second.

[0065] This slow frequency that data can be collected seriously degradesthe accuracy of the velocity calculation The reflection of ultrasonicwaves from the clothes of an occupant, for example, can cause noise orscatter in the position measurement and lead to significant inaccuraciesin a given measurement. When many measurements are taken more rapidly,as in the technique described here, these inaccuracies can be averagedand a significant improvement in the accuracy of the velocitycalculation results.

[0066] The determination of the velocity of the occupant need not bederived from successive distance measurements. A potentially moreaccurate method is to make use of the Doppler effect where the frequencyof the reflected waves differs from the transmitted waves by an amountwhich is proportional to the occupant's velocity. In a preferredembodiment of the present invention, a single ultrasonic transmitter anda separate receiver are used to measure the position of the occupant, bythe travel time of a known signal, and the velocity, by the frequencyshift of that signal. Although the Doppler effect has been used todetermine whether an occupant has fallen asleep as disclosed in the U.S.patent to King referenced above, it has not heretofore been used inconjunction with a position measuring device to determine whether anoccupant is likely to become out of position and thus in danger of beinginjured by a deploying airbag. This combination is particularlyadvantageous since both measurements can be accurately and efficientlydetermined using a single transmitter and receiver pair resulting in alow cost system.

[0067] Another preferred embodiment of this invention makes use of radiowaves and a voltage controlled oscillator (VCO). In this implementation,the frequency of the oscillator is controlled through the use of a phasedetector which adjusts the oscillator frequency so that exactly one halfwave occupies the distance from the transmitter to the receiver viareflection off of the occupant. The adjusted frequency is thus inverselyproportional to the distance from the transmitter to the occupant.Alternately, an FM phase discriminator can be used as known to thoseskilled in the art. These systems could be used in any of the locationsillustrated in FIG. 1.

[0068] It was suggested in the U.S. patent to Mattes et al. discussedabove, that a passive infrared system could be used to determine theposition of an occupant relative to an airbag. Passive infrared measuresthe infrared radiation emitted by the occupant and compares it to thebackground. As such, unless it is coupled with a pattern recognitionsystem, it can best be used to determine that an occupant is movingtoward the airbag since the amount of infrared radiation would then beincreasing. Therefore, it could be used to estimate the velocity of theoccupant but not his/her position relative to the airbag, since theabsolute amount of such radiation will depend on the occupant's size,temperature and clothes as well as on his position. When passiveinfrared is used in conjunction with another distance measuring system,such as the ultrasonic system described above, the combination would becapable of determining both the position and velocity of the occupantrelative to the airbag. Such a combination would be economical sinceonly the simplest circuits would be required. In one implementation, forexample, a group of waves from an ultrasonic transmitter could be sentto an occupant and the reflected group received by a receiver. Thedistance to the occupant would be proportional to the time between thetransmitted and received groups of waves and the velocity determinedfrom the passive infrared system This system could be used in any of thelocations illustrated in FIG. 1 as well as others not illustrated

[0069] Passive infrared could also be used effectively in conjunctionwith a pattern recognition system In this case, the passive infraredradiation emitted from an occupant can be focused onto a CCD array andanalyzed with appropriate pattern recognition circuitry, or software, todetermine the position of the occupant Such a system could be mounted atany of the preferred mounting locations shown in FIG. 1 as well asothers not illustrated

[0070] A transmitter/receiver 215 shown mounted on the cover 220 of theairbag module 216 is shown in FIG. 2. The transmitter/receiver 215 isattached to various electronic circuitry, not shown, by means of wirecable 212. When an airbag 218 deploys, the cover 220 begins movingtoward the driver. If the driver is in close proximity to this coverduring the early stages of deployment, the driver can be seriouslyinjured or even killed. It is important, therefore, to sense theproximity of the driver to the cover and if he or she gets too close, todisable deployment of the airbag 218. An accurate method of obtainingthis information would be to place the distance measuring device ontothe airbag cover 220 as shown in FIG. 2. Appropriate electroniccircuitry can be used to not only determine the actual distance of thedriver from the cover but also his velocity as discussed above. In thismanner, a determination can be made as to where the driver is likely tobe at the time of deployment of the airbag 218 This information can beused most importantly to prevent deployment but also to modify the rateof airbag deployment. In FIG. 2, for one implementation, ultrasonicwaves are transmitted by a transmitter/receiver 215 toward the chest 222of the driver. The reflected waves are then received by the sametransmitter/receiver 215.

[0071] One problem of the system using a sensor 111 in FIG. 1 or sensor215 as shown in FIG. 2 is that a driver may have inadvertently placedhis hand over the transmitter/receiver 111 or 215, thus defeating theoperation of the device. A second confirming transmitter/receiver 110 istherefore placed at some other convenient position such as on the roofor headliner of the passenger compartment as shown in FIG. 3. Thistransmitter/receiver operates in a maimer similar to 111 and 215.

[0072] A more complicated and sophisticated system is shown conceptuallyin FIG. 4 where transmitter/receiver assembly 112 is illustrated. Inthis case, as described briefly above, an infrared transmitter and apair of optical receivers are used to capture the reflection of thepassenger. When this system is used to monitor the driver as shown inFIG. 4, with appropriate circuitry and a microprocessor, the behavior ofthe driver can be monitored Using this system, not only can the positionand velocity of the driver be determined and used in conjunction with anairbag system, but it is also possible to determine whether the driveris falling asleep or exhibiting other potentially dangerous behavior bycomparing portions of his/her image over time. In this case the speed ofthe vehicle can be reduced or the vehicle even stopped if this action isconsidered appropriate. This implementation has the highest probabilityof an unimpeded view of the driver since he/she must have a clear viewthrough the windshield in order to operate the motor vehicle.

[0073] As discussed above, a primary object of this invention is toprovide information as to the location of the driver, or other vehicleoccupant, relative to the airbag, to appropriate circuitry which willprocess this information and make a decision as to whether to preventdeployment of the airbag in a situation where it would otherwise bedeployed, or otherwise affect the time of deployment. One method ofdetermining the position of the driver as discussed above is to actuallymeasure his or her position either using microwaves, optics oracoustics. An alternate approach, which is preferably used to confirmthe measurements made by the systems described above, is to useinformation about the position of the seat and the seatbelt spool out todetermine the likely location of the driver relative to the airbag. Toaccomplish this the length of belt material which has been pulled out ofthe seatbelt retractor can be measured using conventional shaft encodertechnology using either magnetic or optical systems. An example of anoptical encoder is illustrated generally as 501 in FIG. 5, It consistsof an encoder disk 502 and a receptor 503 which sends a signal toappropriate circuitry every time a line on the encoder disk passes bythe receptor.

[0074] In a similar manner, the position of the seat can be determinedthrough either a linear encoder or a potentiometer as illustrated inFIG. 6. In this case, a potentiometer 601 is positioned along the seattrack 602 and a sliding brush assembly 603 is used with appropriatecircuitry to determine the fore and aft location of the seat 610.Naturally, for those seats which permit the seat back angle to beadjusted, a similar measuring system would be used to determine theangle of the seat back. In this manner the position of the seat relativeto the airbag module can be determined. This information can be used inconjunction with the seatbelt spool out sensor to confirm theapproximate position of the chest of the driver relative to the airbagFor most cases the seatbelt spool out sensor would be sufficient to givea good confirming indication of the position of the occupant's chestregardless of the position of the seat and seat back. This is becausethe seatbelt is usually attached to the vehicle at least at one end. Insome cases, especially where the seat back angle can be adjusted,separate retractors would be used for the lap and shoulder portions ofthe seatbelt and the belt would not be permitted to slip through the“D-ring”. The length of belt spooled out from the shoulder beltretractor then becomes a very good confirming measure of the position ofthe occupant's chest.

[0075] The occupant position sensor in any of its various forms can beintegrated into the airbag system circuitry as shovel schematically inFIG. 7. In this example, the occupant position sensors are used as aninput to a smart electronic sensor and diagnostic system. The electronicsensor determines whether the airbag should be deployed based on thevehicle acceleration crash pulse, or crush zone mounted crash sensors,and the occupant position sensor determines whether the occupant is tooclose to the airbag and therefore that the deployment should not takeplace.

[0076] A particular implementation of an occupant position sensor havinga range of from 0 to 2 meters (corresponding to an occupant position offrom 0 to 1 meter since the signal must travel both to and from theoccupant) using infrared is illustrated in the block diagram schematicof FIG. 8. The operation is as follows. A 48 MHz signal, f1, isgenerated by a crystal oscillator 801 and fed into a frequency tripler802 which produces an output signal at 1.44 MHz. The 1.44 MHz signal isthen fed into an infrared diode driver 803 which drives the infrareddiode 804 causing it to emit infrared light modulated at 144 MHz and areference phase angle of zero degrees. The infrared diode 804 isdirected at the vehicle occupant. A second signal f2 having a frequencyof 48 05 MHz, which is slightly greater than f1, is also fed into afrequency tripler 806 to create a frequency of 144.15 MHz. This signalis then fed into a mixer 807 which combines it with the 144 MHz signalfrom frequency tripler 802. The combined signal from the mixer 807 isthen fed to filter 808 which removes all signals except for thedifference, or beat frequency, between 3 times f1 and 3 times f2, of 150kHz. The infrared signal which is reflected from the occupant isreceived by receiver 809 and fed into pre-amplifier 811. This signal hasthe same modulation frequency, 144 MHz, as the transmitted signal butnow is out of phase with the transmitted signal by an angle x due to thepath that the signal took from the transmitter to the occupant and backto the receiver. The output from preamplifier 811 is fed to a secondmixer 812 along with the 144 15 MHz signal from the frequency tripler806. The output from mixer 812 is then amplified by the automatic gainamplifier 813 and fed into filter 814 The filter 814 eliminates allfrequencies except for the 150 kHz difference, or beat, frequency in asimilar maimer as was done by filter 808. The resulting 150 kHzfrequency, however, now has a phase angle x relative to the signal fromfilter 808. Both 150 kHz signals are now fed into a phase detector 815which determines the magnitude of the phase angle x. It can be shownmathematically that, with the above values, the distance from thetransmitting diode to the occupant is x/345.6 where x is measured indegrees and the distance in meters.

[0077] The applications described herein have been illustrated using thedriver of the vehicle. Naturally the same systems of determining theposition of the occupant relative to the airbag apply to the passenger,sometimes requiring minor modifications. It is likely that the sensorrequired triggering time based on the position of the occupant will bedifferent for the driver than for the passenger. Current systems arebased primarily on the driver with the result that the probability ofinjury to the passenger is necessarily increased either by deploying theairbag too late or by failing to deploy the airbag when the position ofthe driver would not warrant it but the passenger's position would. Withthe use of occupant position sensors for both the passenger and driver,the airbag system can be individually optimized for each occupant andresult in further significant injury reduction In particular, either thedriver or passenger system can be disabled if either the driver orpassenger is out of position.

[0078] There is almost always a driver present in vehicles that areinvolved in accidents where an airbag is needed. Only about 30% of thesevehicles, however, have a passenger. If the passenger is not present,there is usually no need to deploy the passenger side airbag. Theoccupant position sensor, when used for the passenger side with properpattern recognition circuitry, can also ascertain whether or not theseat is occupied, and if not, can disable the deployment of thepassenger side airbag and thereby save the cost of its replacement Asophisticated pattern recognition system could even distinguish betweenan occupant and a bag of groceries, for example Finally, there has beenmuch written about the out of position child who is standing orotherwise positioned adjacent to the airbag, perhaps due to pre-crashbraking Naturally, the occupant position sensor described herein canprevent the deployment of the airbag in this situation.

[0079]FIG. 9 shows a flowchart of the manner in which an airbag or otheroccupant restraint or protection device may be controlled based on theposition of an occupant. The position of the occupant is determined at902 by any one of a variety of different occupant sensing systemsincluding a system designed to receive waves, energy or radiation from aspace in a passenger compartment of the vehicle occupied by theoccupant, and which also optionally transmit such waves, energy orradiation. A camera or other device for obtaining images, two orthree-dimensional, of a passenger compartment of the vehicle occupied bythe occupant and analyzing the images may be used. The image device mayinclude a focusing system which focuses the images onto optical arraysand analyzes the focused images A device which moves a beam of radiationthrough a passenger compartment of the vehicle occupied by the occupantmay also be used, e.g., a scanning type of system. An electric fieldsensor operative in a seat occupied by the occupant and a capacitancesensor operative in the seat occupied by the occupant may also be used.

[0080] The probability of a crash is assessed at 904, e.g., by a crashsensor. Deployment of the airbag is then enabled at 906 in considerationof the determined position of the occupant and the assessed probabilitythat a crash is occurring. A sensor algorithm may be used to receive theinput from the crash sensor and occupant position determining system anddirect or control deployment of the airbag based thereon. Moreparticularly, in another embodiment, the assessed probability isanalyzed, e g, by the sensor algorithm, relative to a pre-determinedthreshold at 908 whereby a determination is made at 910 if the assessedprobability is greater than the threshold. If not, the probability ofthe crash is again assessed until the probability of a crash is greaterthan the threshold.

[0081] Optionally, the threshold is set or adjusted at 912 based on thedetermined position of the occupant Deployment of the airbag can entaildisabling deployment of the airbag when the determined position is tooclose to the airbag, determining the rate at which the airbag isinflated based on the determined position of the occupant and/ordetermining the time in which the airbag is deployed based on thedetermined position of the occupant.

[0082] Disclosed above is an airbag system for inflation and deploymentof an air bag in front of the passenger during a collision whichcomprises an air bag, an inflator connected to the air bag andstructured and arranged to inflate the air bag with a gas, a passengersensor system mounted at least partially adjacent to or on the interiorroof of the vehicle, and a microprocessor electrically connected to thesensor system and to the inflator. The sensor system continuously sensesthe position of the passenger and generates electrical output indicativeof the position of the passenger. The microprocessor compares andperforms an analysis of the electrical output from the sensor system andactivates the inflator to inflate and deploy the air bag when theanalysis indicates that the vehicle is involved in a collision and thatdeployment of the air bag would likely reduce a risk of serious injuryto the passenger which would exist absent deployment of the air bag andlikely would not present an increased risk of injury to the passengerresulting from deployment of the air bag.

[0083] The sensor system might be designed to continuously senseposition of the passenger relative to the air bag. The sensor system maycomprise an array of passenger proximity sensors, each sensing distancefrom a passenger to the proximity sensor. In this case, themicroprocessor determines the passenger's position by determining eachof the distances and then triangulating the distances from the passengerto each of the proximity sensors. The microprocessor can include memoryin which the positions of the passenger over some interval of time arestored. The sensor system may be particularly sensitive to the positionof the head of the passenger. As to the position of the sensor system,it may be arranged on the rear view mirror, on the roof, on a windshieldheader of the vehicle, positioned to be operative rearward and/or at afront of the passenger compartment.

[0084] Another embodiment of an airbag control system comprises a sensorsystem mounted adjacent to or on an interior roof of the vehicle and amicroprocessor connected to the sensor system and to an inflator of theair bag. The sensor system senses the position of the occupant withrespect to the passenger compartment of the vehicle and generates outputindicative of the position of the occupant. The microprocessor comparesand performs an analysis of the output from the sensor system andactivate the inflator to inflate the air bag when the analysis indicatesthat the vehicle is involved in a collision and deployment of the airbag is desired.

[0085] The sensor system may comprise an array of occupant proximitysensors, each sensing distance from the occupant to that proximitysensor. The microprocessor determines the occupant's position bydetermining each distance and triangulating the distances from theoccupant to each proximity sensor. The microprocessor includes memory inwhich the positions of the occupant over some interval of time arestored. The sensor system may be particularly sensitive to the positionof the head of the passenger. As to the position of the sensor system,it may be arranged on the rear view mirror, on the roof, on a windshieldheader of the vehicle, positioned to be operative rearward and/or at afront of the passenger compartment Also disclosed herein is a method ofdisabling an airbag system for a seating position within a motor vehiclewhich comprises the steps of providing to a roof above the seatingposition one or more electromagnetic wave occupant sensors, detectingpresence or absence of an occupant of the seating position using theelectromagnetic wave occupant sensor(s), disabling the airbag system ifthe seating position is unoccupied, detecting proximity of an occupantto the airbag door if the seating position is occupied and disabling theairbag system if the occupant is closer to the airbag door than apredetermined distance. The airbag deployment parameters, e.g.,inflation rate and time of deployment, may be modified to adjustinflation of the airbag according to proximity of the occupant to theairbag door The presence or absence of the occupant can be detectedusing pattern recognition techniques to process the waves received bythe electromagnetic wave-occupant sensor(s).

[0086] An apparatus for disabling an airbag system for a seatingposition within a motor vehicle comprises one or more electromagneticwave occupant sensors proximate a roof above the seating position, meansfor detecting presence or absence of an occupant of the seating positionusing the electromagnetic wave occupant sensor(s), means for disablingthe airbag system if the seating position is unoccupied, means fordetecting proximity of an occupant to the airbag door if the seatingposition is occupied and means for disabling the airbag system if theoccupant is closer to the airbag door than a predetermined distanceAlso, means for modifying airbag deployment parameters to adjustinflation of the airbag according to proximity of the occupant to theairbag door may be provided and may constitute a sensor algorithmresident in a crash sensor and diagnostic circuitry The means fordetecting presence or absence of the occupant may comprises a processorutilizing pattern recognition techniques to process the waves receivedby the electromagnetic wave-occupant sensor(s).

[0087] The motor vehicle air bag system for inflation and deployment ofan air bag in front of a passenger in a motor vehicle during a collisionin accordance with the invention comprises an air bag, inflation meansconnected to the airbag for inflating the same with a gas, passengersensor means mounted adjacent to the interior roof of the vehicle forcontinuously sensing the position of a passenger with respect to thepassenger compartment and for generating electrical output indicative ofthe position of the passenger and microprocessor means electricallyconnected to the passenger sensor means and to the inflation means. Themicroprocessor means compare and perform an analysis of the electricaloutput from the passenger sensor means and activate the inflation meansto inflate and deploy the air bag when the analysis indicates that thevehicle is involved in a collision and that deployment of the air bagwould likely reduce a risk of serious injury to the passenger whichwould exist absent deployment of the air bag and likely would notpresent an increased risk of injury to the passenger resulting fromdeployment of the air bag. In certain embodiments, the passenger sensormeans is a means particularly sensitive to the position of the head ofthe passenger The microprocessor means may include memory means forstoring the positions of the passenger over some interval of time Thepassenger sensor means may comprise an array of passenger proximitysensor means for sensing distance from a passenger to each of thepassenger proximity sensor means In this case, the microprocessor meansincludes means for determining passenger position by determining each ofthese distances and means for triangulation analysis of the distancesfrom the passenger to each passenger proximity sensor means to determinethe position of the passenger.

[0088] There has thus been shown and described an occupant positionsensor which fulfills all the objects and advantages sought after Manychanges, modifications, variations and other uses and applications ofthe subject invention will, however, become apparent to those skilled inthe art after considering this specification and the accompanyingdrawings which disclose the preferred embodiments thereof All suchchanges, modifications, variations and other uses and applications whichdo not depart from the spirit and scope of the invention are deemed tobe covered by the invention which is limited only by the followingclaims.

What is claimed is:
 1. A method for controlling deployment of an airbag, comprising the steps of: determining the position of an occupant to be protected by deployment of the airbag; assessing the probability that a crash requiring deployment of the airbag is occurring; and enabling deployment of the airbag in consideration of the determined position of the occupant and the assessed probability that a crash is occurring.
 2. The method of claim 1, wherein the step of enabling deployment of the airbag comprises the steps of analyzing the assessed probability relative to a pre-determined threshold whereby deployment of the airbag is enabled only when the assessed probability is greater than the threshold.
 3. The method of claim 2, further comprising the step of adjusting the threshold based on the determined position of the occupant.
 4. The method of claim 1, wherein the step of determining the position of the occupant comprises the step of receiving waves from a space in a passenger compartment of the vehicle occupied by the occupant.
 5. The method of claim 1, wherein the step of determining the position of the occupant comprises the step of transmitting waves to impact the occupant; receiving waves after impact with the occupant and measuring time between transmission and reception of the waves.
 6. The method of claim 1, wherein the step of determining the position of the occupant comprises the steps of obtaining images of a passenger compartment of the vehicle occupied by the occupant and analyzing the images.
 7. The method of claim 1, wherein the step of determining the position of the occupant comprises the steps of obtaining images of a passenger compartment of the vehicle occupied by the occupant, focusing the images onto optical arrays and analyzing the focused images.
 8. The method of claim 1, wherein the step of determining the position of the occupant comprises the steps of moving a beam of radiation through a passenger compartment of the vehicle occupied by the occupant.
 9. The method of claim 1, wherein the step of determining the position of the occupant comprises the step of transmitting ultrasonic waves to impact the occupant; receiving ultrasonic waves after reflection by the occupant and measuring time between transmission and reception of the waves.
 10. The method of claim 1, wherein the step of determining the position of the occupant comprises the step of receiving infrared radiation from a space in a passenger compartment of the vehicle occupied by the occupant.
 11. The method of claim 1, wherein the step of determining the position of the occupant comprises the step of transmitting radar waves to impact the occupant; receiving radar waves after reflection by the occupant and measuring time between transmission and reception of the waves.
 12. The method of claim 1, wherein the step of determining the position of the occupant comprises the steps of obtaining three-dimensional images of a passenger compartment of the vehicle occupied by the occupant and analyzing the images.
 13. The method of claim 1, wherein the step of determining the position of the occupant comprises the steps of arranging an electric field sensor operative in a seat occupied by the occupant.
 14. The method of claim 1, wherein the step of determining the position of the occupant comprises the steps of arranging a capacitance sensor operative in a seat occupied by the occupant.
 15. The method of claim 1, further comprising the step of disabling deployment of the airbag when the determined position is too close to the airbag.
 16. The method of claim 1, further comprising the step of determining the rate at which the airbag is inflated based on the determined position of the occupant.
 17. The method of claim 1, further comprising the step of determining the time in which the airbag is deployed based on the determined position of the occupant.
 18. A method for controlling deployment of an airbag, comprising the steps of: determining the position of an occupant to be protected by deployment of the airbag; and adjusting a threshold used in a sensor algorithm which enables or suppresses deployment of the airbag based on the determined position of the occupant
 19. The method of claim 18, further comprising the steps of: assessing the probability that a crash requiring deployment of the airbag is occurring; and analyzing the assessed probability relative to the threshold whereby deployment of the airbag is enabled only when the assessed probability is greater than the threshold.
 20. The method of claim 18, wherein the step of determining the position of the occupant comprises the step of receiving waves from a space in a passenger compartment of the vehicle occupied by the occupant
 21. The method of claim 18, wherein the step of determining the position of the occupant comprises the step of transmitting waves to impact the occupant; receiving waves after impact with the occupant and measuring time between transmission and reception of the waves.
 22. The method of claim 18, wherein the step of determining the position of the occupant comprises the steps of obtaining images of a passenger compartment of the vehicle occupied by the occupant and analyzing the images.
 23. The method of claim 18, wherein the step of determining the position of the occupant comprises the steps of obtaining images of a passenger compartment of the vehicle occupied by the occupant, focusing the images onto optical arrays and analyzing the focused images.
 24. The method of claim 18, wherein the step of determining the position of the occupant comprises the steps of moving a beam of radiation through a passenger compartment of the vehicle occupied by the occupant.
 25. The method of claim 18, wherein the step of determining the position of the occupant comprises the step of transmitting ultrasonic waves to impact the occupant; receiving ultrasonic waves after reflection by the occupant and measuring time between transmission and reception of the waves.
 26. The method of claim 18, wherein the step of determining the position of the occupant comprises the step of receiving infrared radiation from a space in a passenger compartment of the vehicle occupied by the occupant
 27. The method of claim 18, wherein the step of determining the position of the occupant comprises the step of transmitting radar waves to impact the occupant; receiving radar waves after reflection by the occupant and measuring time between transmission and reception of the waves.
 28. The method of claim 18, wherein the step of determining the position of the occupant comprises the steps of obtaining three-dimensional images of a passenger compartment of the vehicle occupied by the occupant and analyzing the images.
 29. The method of claim 18, wherein the step of determining the position of the occupant comprises the steps of arranging an electric field sensor operative in a seat occupied by the occupant.
 30. The method of claim 18, wherein the step of determining the position of the occupant comprises the steps of arranging a capacitance sensor operative in a seat occupied by the occupant.
 31. The method of claim 18, further comprising the step of disabling deployment of the airbag when the determined position is too close to the airbag.
 32. The method of claim 18, further comprising the step of determining the rate at which the airbag is inflated based on the determined position of the occupant.
 33. The method of claim 18, further comprising the step of determining the time in which the airbag is deployed based on the determined position of the occupant.
 34. A system for controlling deployment of an airbag, comprising: determining means for determining the position of an occupant to be protected by deployment of the airbag; sensor means for assessing the probability that a crash requiring deployment of the airbag is occurring; and circuit means coupled to said determining means, said sensor means and the airbag for enabling deployment of the airbag in consideration of the determined position of the occupant and the assessed probability that a crash is occurring.
 35. The system of claim 34, wherein said circuit means are structured and arranged to analyze the assessed probability relative to a pre-determined threshold whereby deployment of the airbag is enabled only when the assessed probability is greater than the threshold.
 36. The system of claim 35, wherein said circuit means are arranged to adjust the threshold based on the determined position of the occupant
 37. The system of claim 34, wherein said determining means are arranged to receive waves from a space in a passenger compartment of the vehicle occupied by the occupant
 38. The system of claim 34, wherein said determining means are arranged to transmit waves to impact the occupant, receive waves after impact with the occupant and measure the time between transmission and reception of the waves.
 39. The system of claim 34, wherein said determining means comprise means for obtaining images of a passenger compartment of the vehicle occupied by the occupant and analyzing the images.
 40. The system of claim 34, wherein said determining means comprise means for obtaining images of a passenger compartment of the vehicle occupied by the occupant, focusing the images onto optical arrays and analyzing the focused images
 41. The system of claim 34, wherein said determining means comprise means for moving a beam of radiation through a passenger compartment of the vehicle occupied by the occupant.
 42. The system of claim 34, wherein said determining means comprise means for transmitting ultrasonic waves to impact the occupant, receiving ultrasonic waves after reflection by the occupant and measuring time between transmission and reception of the waves.
 43. The system of claim 34, wherein said determining means are arranged to receive infrared radiation from a space in a passenger compartment of the vehicle occupied by the occupant.
 44. The system of claim 34, wherein said determining means comprise means for transmitting radar waves to impact the occupant, receiving radar waves after reflection by the occupant and measuring time between transmission and reception of the waves.
 45. The system of claim 34, wherein said determining means comprise means for obtaining three-dimensional images of a passenger compartment of the vehicle occupied by the occupant and analyzing the images.
 46. The system of claim 34, wherein said determining means comprise an electric field sensor operative in a seat occupied by the occupant
 47. The system of claim 34, wherein said determining means comprise a capacitance sensor operative in a scat occupied by the occupant.
 48. The system of claim 34, wherein said circuit means are arranged to disable deployment of the airbag when the determined position is too close to the airbag.
 49. The system of claim 34, wherein the airbag has an adjustable inflation rate, said circuit means are arranged to determine the rate at which the airbag is inflated based on the determined position of the occupant
 50. The system of claim 34, wherein the airbag has an adjustable deployment time, said circuit means are arranged to determine the time in which the airbag is inflated based on the determined position of the occupant.
 51. A system for controlling deployment of an airbag, comprising: a crash sensor for providing information on a crash involving the vehicle; a position determining arrangement for determining the position of an occupant to be protected by deployment of the airbag; and a circuit coupled to the airbag, said crash sensor and said position determining arrangement and arranged to issue a deployment signal to the airbag to cause deployment of the airbag, said circuit being arranged to consider a deployment threshold which varies based on the determined position of the occupant
 52. The system of claim 51, wherein said circuit is arranged to assess the probability that a crash requiring deployment of the airbag is occurring and analyze the assessed probability relative to the threshold whereby deployment of the airbag is enabled only when the assessed probability is greater than the threshold.
 53. The system of claim 51, wherein said determining means are arranged to receive waves from a space in a passenger compartment of the vehicle occupied by the occupant.
 54. The system of claim 51, wherein said determining means are arranged to transmit waves to impact the occupant, receive waves after impact with the occupant and measure the time between transmission and reception of the waves.
 55. The system of claim 51, wherein said determining means comprise means for obtaining images of a passenger compartment of the vehicle occupied by the occupant and analyzing the images.
 56. The system of claim 51, wherein said determining means comprise means for obtaining images of a passenger compartment of the vehicle occupied by the occupant, focusing the images onto optical arrays and analyzing the focused images
 57. The system of claim 51, wherein said determining means comprise means for moving a beam of radiation through a passenger compartment of the vehicle occupied by the occupant.
 58. The system of claim 51, wherein said determining means comprise means for transmitting ultrasonic waves to impact the occupant, receiving ultrasonic waves after reflection by the occupant and measuring time between transmission and reception of the waves
 59. The system of claim 51, wherein said determining means are arranged to receive infrared radiation from a space in a passenger compartment of the vehicle occupied by the occupant.
 60. The system of claim 51, wherein said determining means comprise means for transmitting radar waves to impact the occupant, receiving radar waves after reflection by the occupant and measuring time between transmission and reception of the waves.
 61. The system of claim 51, wherein said determining means comprise means for obtaining three-dimensional images of a passenger compartment of the vehicle occupied by the occupant and analyzing the images.
 62. The system of claim 51, wherein said determining means comprise an electric field sensor operative in a seat occupied by the occupant
 63. The system of claim 51, wherein said determining means comprise a capacitance sensor operative in a seat occupied by the occupant.
 64. The system of claim 51, wherein said circuit is arranged to disable deployment of the airbag when the determined position is too close to the airbag.
 65. The system of claim 51, wherein the airbag has an adjustable inflation rate, said circuit being arranged to determine the rate at which the airbag is inflated based on the determined position of the occupant.
 66. The system of claim 51, wherein the airbag has an adjustable deployment time, said circuit being arranged to determine the time in which the airbag is inflated based on the determined position of the occupant. 